Pumps for transferring fluids intended for human consumption

ABSTRACT

Pumps are provided for transferring fluids between tanks and other types of vessels. The pumps include a rotating impeller that pumps the fluid, and an electric motor that imparts rotation to the impeller. The impeller is mounted for rotation on a shaft by way of a bushing. The bushing is made of a material suitable for contact with food products intended for human consumption. Also, the material can withstand the elevated temperatures that arise in the bushing when the pump is run in a dry condition, i.e., without any fluid passing through the pump.

This application claims the benefit of priority to U.S. Provisional Patent Application No. 62/765,061, filed Aug. 16, 2018, the disclosure of which is hereby incorporated by reference in its entirety.

BACKGROUND

Home brewing of beer has grown, and continues to grow in popularity. Home brewing refers to the production of relatively small quantities of beer, usually by a hobbyist in his or her own home or other non-industrial setting. During a typical home brewing process, fluids need to be transferred between the various pieces equipment used in the overall brewing process. For example, wort, i.e., the liquid extracted from the mashing process, needs to be transferred between the various pieces of equipment used to process the wort, e.g., a kettle, separator, fermenter, etc.

Wort and other fluids typically are transferred during the home brewing process using electrically-powered pumps. These pumps usually include an impeller mounted for rotation on a stationary shaft; a pump housing that encloses the impeller and directs flow to and from the impeller; and a small, e.g., 1/20 horsepower, electric motor that is coupled to, and imparts rotation to the impeller. The rotating impeller receives fluid from a source, such as a supplying vessel, connected to the inlet of the housing. The impeller pumps the fluid to a receiving vessel by way of the housing outlet.

The impeller typically is molded from a thermoplastic or thermosetting material such as polyphenylene sulfide, PPS. Because the impeller directly contacts the wort or other fluid, which after further processing will be consumed by humans, the impeller material needs to be a food-grade material that complies with the food-contact regulations of the U.S. Food and Drug Administration (FDA) or other controlling authority.

The pumps used in home brewing operations usually are activated on a manual, i.e., non-automatic, basis. Thus, it is common for such pumps to be inadvertently operated in a dry condition, i.e., without any fluid flow, due to factors such as operator inattentiveness, difficulty in determining when the supplying vessel has run dry, unintentional movement of the supply line out of the fluid being transferred, etc. The fluid flow over the impeller normally acts as a heat-transfer medium that cools the impeller by drawing away heat generated by the friction between the impeller, and the static shaft upon which the impeller rotates. Thus, the impeller can be subjected to elevated temperatures in the absence of such flow. These elevated temperatures, in turn, can cause the impeller to substantially expand and melt, which typically results in seizure of the bushing on the shaft and irreparable damage to the bushing, necessitating partial disassembly of the pump and replacement of the impeller. Such damage can occur in very short time period, e.g., one minute or less, when a pump is operating with no fluid flow.

Substituting a more heat-resistant material for the thermoplastic or thermosetting material from which the impeller typically is formed can present substantial difficulties. For example, any substitute material needs to be suitable for contact with food products, and capable of being molded or otherwise formed into the multi-bladed impeller in an economical manner Forming the impeller with a non-plastic, heat-resistant insert, i.e., changing the impeller from a one-piece to a two-piece configuration, also can present substantial difficulties. For example, any such insert also needs to be suitable for contact with food products; and the substantial volumetric shrinkage that typically occurs when molded plastic cools and solidifies can crack, distort, and otherwise damage an insert around which the impeller is formed.

SUMMARY

In one aspect, the disclosed technology relates to pumps for transferring fluids. The pumps include an electric motor comprising a rotatable output shaft, and a pump housing having an inlet and an outlet. The pumps also include a shaft mounted on the pump housing, and an impeller assembly. The impeller assembly has a bushing mounted for rotation on the shaft and made of a resin-impregnated, carbon-graphite material. The impeller assembly also includes an impeller having a body and blades attached to the body. The impeller is mounted on the bushing, and the impeller is magnetically coupled the output shaft of the electric motor so that the output shaft is operable to impart rotation to the impeller when the output shaft rotates. The impeller is configured to pump the fluids between the inlet and the outlet of the housing as the impeller rotates.

In another aspect, the disclosed technology relates to pumps for transferring fluids. The pumps include an electric motor comprising a rotatable output shaft, and a pump housing having an inlet and an outlet. The pumps also include a shaft mounted on the pump housing, and an impeller assembly. The impeller assembly has a bushing mounted for rotation on the shaft. The bushing is made of a food-grade material having a maximum operating temperature of at least about 500° F. The impeller assembly also includes an impeller having a body and blades attached to the body. The impeller is mounted on the bushing, and the impeller is coupled the output shaft of the electric motor so that the output shaft is operable to impart rotation to the impeller when the output shaft rotates. The impeller is configured to pump the fluids between the inlet and the outlet of the housing as the impeller rotates.

In another aspect, the disclosed technology relates to processes for producing an impeller assembly for a pump for transferring fluids. The processes include forming a bushing from a resin-impregnated, carbon-graphite material; and molding an impeller over the bushing.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will be described with reference to the following drawing figures, in which like reference numerals represent like parts and assemblies throughout the several views.

FIG. 1 is a perspective view of a pump for transferring fluids intended for human consumption;

FIG. 2 is an exploded perspective view of the pump shown in FIG. 1.

FIG. 3 is a side view of the pump shown in FIGS. 1 and 2.

FIG. 4 is a front view of the pump shown in FIGS. 1-3.

FIG. 5A is a front perspective view of a bushing of the pump shown in FIGS. 1-4.

FIG. 5B is a magnified view of the area designated “A” in FIG. 5A.

FIG. 5C is a front view of the bushing shown in FIGS. 5A and 5B.

FIG. 6A is a front perspective view of an impeller assembly of the pump shown in FIGS. 1-5C.

FIG. 6B is a rear view of the impeller assembly shown in FIG. 6A.

FIG. 7 is an exploded perspective view of an alternative embodiment of the pump shown in FIGS. 1-6B.

FIG. 8A is a front view of another alternative embodiment of the pump shown in FIGS. 1-6B.

FIG. 8B is a side view of the pump shown in FIG. 8A.

DETAILED DESCRIPTION

The inventive concepts are described with reference to the attached figures. The figures are not drawn to scale and are provided merely to illustrate the instant inventive concepts. The figures do not limit the scope of the present disclosure. Several aspects of the inventive concepts are described below with reference to example applications for illustration. It should be understood that numerous specific details, relationships, and methods are set forth to provide a full understanding of the inventive concepts. One having ordinary skill in the relevant art, however, will readily recognize that the inventive concepts can be practiced without one or more of the specific details or with other methods. In other instances, well-known structures or operation are not shown in detail to avoid obscuring the inventive concepts.

FIGS. 1-6B depict a pump 10 and various components thereof. The pump 10 can be used to transfer fluids intended for human consumption. For example, the pump 10 can be used during the brewing of beer to transfer wort, i.e., the liquid extracted from the mashing process, between the various pieces of equipment used to process the wort, e.g., a kettle, separator, fermenter, etc. This particular application is described for exemplary purposes only; the pump 10 can be used to transfer other types of fluids, in other applications. Also, details of the overall structure and operation of the pump 10 are presented for exemplary purposes only. The inventive principles disclosed herein can be applied to other types of pumps.

The pump 10 comprises an electric motor 14, a head assembly 16, and a magnet 18, as shown in FIGS. 1-4. The head assembly 16 comprises a housing 20, and an impeller assembly 21 located within the housing 20. The impeller assembly 21 comprises a rigid impeller 22, a bushing 44, and a magnetic sleeve 23.

The housing 20 includes a front cover plate 26, a rear cover plate 28 configured to mate with the front cover plate 26, and an O-ring gasket 30 that seals the interface between the front cover plate 26 and the rear cover plate 28. The front cover plate 26 can be attached to the rear cover plate 28 by screws or other suitable means. The front cover plate 26 and the rear cover plate 28 form a volume 32 that houses the impeller assembly 21. The front cover plate 26 and the rear cover plate 28 are formed from stainless steel. The front cover plate 26 and the rear cover plate 28 can be constructed from other suitable materials, such as polysulfone and other thermoplastic and thermosetting materials, in alternative embodiments.

The head assembly 16 has a center inlet configuration. In particular, the front cover plate 26 has an inlet 34 located in the approximate center of the front cover plate 26, as can be seen in FIGS. 1-4. The inlet 34 is in fluid communication with the volume 32, and directs the wort or other incoming fluid into the volume 32. The inlet 34 is oriented so that the incoming fluid flows through the inlet 34 in a direction approximately parallel to the axis of rotation of the impeller 22, as denoted by the arrow 37 in FIGS. 1 and 3. The inlet 34 has internal threads, for connecting the head assembly 16 to hoses, piping, or other means for routing the incoming fluid to the pump 10.

The outlet 36 is located along the outer periphery of the rear cover plate 28. The outlet 36 is in fluid communication with the volume 32. The impeller 22 rotates within the volume 32 at, for example, about 3,500 revolutions per minute. The rotating impeller 22, through centrifugal action, pumps the wort or other fluid out of the head assembly 16 by way of the outlet 36, in a direction substantially perpendicular to the axis of rotation of the impeller 22 as denoted by the arrow 39 in FIGS. 1, 3, and 4. The outlet 36 has external threads for connecting the head assembly 16 to hoses, piping, or other means for routing the fluid from the pump 10, to the downstream vessel.

The front cover plate 26 includes a mounting bracket 40 that spans the inner, or downstream end of the inlet 34, as shown in FIG. 3. The head assembly 16 further comprises a shaft 42, depicted in FIG. 2. An end of the shaft 42 is securely mounted in a through hole formed in the bracket 40, using an interference fit or other suitable means. The impeller assembly 21 is mounted for rotation on the shaft 42 by way of the bushing 44, details of which are presented below.

The inventive principles disclosed herein can be applied to pumps having an in-line configuration, in lieu of the center-inlet configuration of the pump 10. For example, FIGS. 8A and 8B depict an alternative embodiment of the pump 10 in the form of a pump 10 b. The pump 10 b comprises a head assembly 16 a having an in-line configuration. Components of the pump 10 b that are substantially identical to those of the pump 10 are denoted by identical reference characters in the figures. As can be seen in FIGS. 8A and 8B, the inlet 34 a and the outlet 34 b of the head assembly 16 a are in line, i.e., are oriented in substantially the same direction. The head assembly 16 a can be equipped with the impeller assembly 21 of the pump 10, or variants thereof.

The motor 14 is a TEFC, or totally-enclosed, fan-cooled motor; the inventive principles disclosed herein can be applied to other types of motors, such as ODP, or open drift proof motors. For example, FIG. 7 depicts an alternative embodiment of the pump 10 in the form of a pump 10 a having an ODP motor 14 a. Components of the pump 10 a that are substantially identical to those of the pump 10 are denoted by identical reference characters in the figures. The motor 14 can have a power rating of 1/20 horsepower; motors having other power ratings can be used in alternative embodiments.

Referring to FIGS. 1-3, the motor 14 has an output shaft 19, a magnet housing 54, and an outer casing 56. A first end of the magnet housing 54 is secured to the outer casing 56. The output shaft 19 is mechanically connected to the rotor of the motor 14, and extends into the magnet housing 54.

The magnet 18 is cup-shaped, and is positioned within the magnet housing 54. The closed end of the magnet 18 is securely connected to the output shaft 19 by a screw or other suitable means, so that the output shaft 19 transfers torque generated by the motor 14 to the magnet 18. A clearance exists between the outer periphery of the magnet 18 and the adjacent surface of the magnet housing 54, so that the magnet 18 can rotate in relation to the magnet housing 54 and the outer casing 56.

The head assembly 16 also includes a ring-shaped rear thrust bushing (not shown). The thrust bushing is secured to an inwardly-facing, rearward surface of a cup-shaped portion 58 of the rear cover plate 28. The thrust bushing contacts the rearward end of the magnetic sleeve 23, and thereby restrains the impeller assembly 21 from rearward movement during operation of the pump 10.

The head assembly 16 further comprises a front thrust bushing 62, shown in FIG. 2. The front thrust bushing 62 is positioned on the shaft 42, between the bushing 44 and the mounting bracket 40. The front thrust bushing 62 contacts a forward end 46 a of the bushing 44, and thereby restrains the impeller assembly 21 from forward movement during operation of the pump 10.

Referring to FIGS. 2, 6A, and 6B, the impeller 22 has a body 25, and four blades 27. The blades 27 are formed unitarily with the body 25, and extend radially outward from a forward end of the body 25. The impeller 22 can have more, or less than four blades 27 in alternative embodiments. The impeller 22 can be formed from a food grade plastic such as PPS; other thermoplastic and thermosetting materials can be used in the alternative. The term “food grade,” as used herein, means that the noted material complies with the applicable food-contact regulations of the FDA or other regulatory authorities.

Referring to FIGS. 6A and 6B, the magnetic sleeve 23 is approximately cup-shaped; and includes a cylindrical side portion 50, and an adjoining end portion 51. The magnetic sleeve 23 is positioned over, and is secured to the body 25 of the impeller 22. The sleeve 23 can be secured to the impeller 22 by an interference fit or other suitable means. The sleeve 23 is formed from a suitable magnetic material such as magnetized stainless steel, lined on its interior with rare earth magnets.

Referring to FIG. 2, the magnetic sleeve 23 is located within the cup-shaped portion 58 of the rear cover plate 28 of the housing 20. A clearance exists between the outer periphery of the sleeve 23 and the adjacent surfaces of the portion 58 so that the sleeve 23, which is mounted on the shaft 42 by way of the impeller 22 and the bushing 44, can rotate in relation to the housing 20.

The cup-shaped portion 58 of the rear cover plate 28 is positioned within the magnet 18, so that the magnet 18 is located within the magnetic field of the magnetic sleeve 23, and the magnetic sleeve 23 is located within the magnetic field of the magnet 18. A clearance exists between the outer periphery of the cup-shaped portion 58 and the adjacent surfaces of the magnet 18, so that the magnet 18 can rotate in relation to the rear cover plate 28. Because the magnet 18 is magnetically coupled to the magnetic sleeve 23, rotation of the magnet 18 by the motor 14 causes the magnetic sleeve 23 to undergo a corresponding rotation, which in turn rotates the impeller 22. The magnet 18, magnetic sleeve 23, and motor 14 thus function as a magnetic drive for the impeller 22. The impeller 22 can be driven by a means other than a magnetic drive in alternative embodiments.

Referring to FIGS. 5A-5C, the bushing 44 has a cylindrical shape defined, in part, by a cylindrical outer surface 49. A cylindrical passage 45 is formed within the bushing 44. The passage 45 extends along the longitudinal centerline of the bushing 44, between the forward end 46 a and a rearward end 46 b of the bushing 44. The passage 45 receives the shaft 42. The diameter of the passage 45 is selected so that the bushing 44 fits over the shaft 42 with a minimal radial clearance, e.g., about 0.006 inch, allowing the bushing 44 to rotate freely on the shaft 42 without excessive wobble.

Two shallow, diametrically-opposed slots 47 are formed in the forward end 46 a of the bushing 44, adjacent the passage 45. The slots 47 can provide a path for a portion of the liquid passing over the impeller 22 to reach, and cool the shaft 42. The bushing 44 has a chamfered surface 48, visible in FIG. 5B, located between the forward end 46 a and the side surface 49. The chamfered surface 48 is believed to reduce the potential for localized chipping and cracking of the bushing 44.

The bushing 44 is formed from a resin-impregnated, carbon-graphite material. The material is a food-grade material. The use of a food-grade material maintains the suitability of the pump 10 for use in applications, such as the brewing of beer, in which the fluid passing through the pump 10 is intended for human consumption.

In addition to being a food-grade material, the material from which the bushing 44 is formed is oil free, self-lubricating, and can withstand the relatively high temperatures that develop within the bushing 44 when the pump 10 is run in a dry condition, i.e., without any fluid being supplied to the inlet 34 of the head assembly 16. In particular, the bushing 44, unlike conventional food-grade impellers formed from thermoplastic and thermosetting materials such as polyphenylene sulfide, will not substantially expand and will not melt when subjected to the elevated temperatures that can occur within the bushing 44 when the pump 10 is run in a dry condition. Such elevated temperatures can result from the friction between the rotating bushing 44 and the stationary shaft 42; and the absence of fluid flow over the bushing 44, which normally acts as a heat-transfer medium that cools the bushing 44. The expansion and/or melting of a conventional FDA-complaint plastic impeller when subjected to elevated temperatures typically results in seizure of the bushing on its shaft and irreparable damage to the bushing, necessitating replacement of the entire impeller. Such damage can occur in very short time period, e.g., one minute or less, when a pump is operating with no fluid flow.

The bushing 44 can be formed, for example, from METCAR® Grade M-100 resin-impregnated, carbon-graphite material, available from Metallized Carbon Corporation of Ossining, N.Y. In addition to being a food-grade material that complies with the food-contact regulations of the FDA, this material can have the following physical properties: temperature limit in oxidizing atmosphere: 500° F.; temperature limit in non-oxidizing atmosphere: 500° F.; thermal conductivity: 8 BTU/hr/ft²/° F./ft; coefficient of thermal expansion: 2.9 in/in/° F./10-6; modulus of elasticity: 3.1 psi×106; tensile strength: 6,000 PSI; compressive strength: 27,000 PSI; transverse strength: 9,000 PSI; apparent density: 1.85; and hardness: 80 (Shore scleroscope). These values are presented for exemplary purposes only; the material from which the bushing 44 is formed can have different properties in alternative embodiments.

The outside diameter of the shaft 42 is about 0.250 inch. The bushing 44 can have an inner diameter of about 0.256 inch +/−0.001 inch; an outer diameter of about 0.431 inch +/−0.005 inch; and a length of about 1.096 inch +/−0.005 inch. In alternative embodiments, the bushing 44 can have an inner diameter of about 0.256 inch +/−0.001 inch; an outer diameter of about 0.571 inch +/−0.005 inch; and a length of about 1.700 inch +/−0.005 inch. These dimensions are presented for exemplary purposes only; the shaft 42 and the bushing 44 can have other dimensions in alternative embodiments.

As discussed above, it is common for pumps such as the pump 10 to be inadvertently operated in a dry condition when the pump 10 is used in home brewing operations and other non-automated processes in which the operator uses a manually activated pump to transfer fluid between different vessels. Also, pumps often are run in a dry condition when the fluid level in the supplying vessel approaches empty. Operating a pump with a conventional FDA-compliant plastic bushing in a dry condition for even a short amount of time typically will result in heat damage necessitating replacement of the bushing. Thus, the use of the bushing 44 can help avoid the time, effort, delay, and expense associated with replacing a bushing that has been damaged or otherwise rendered unusable by operating a pump in a dry condition; while allowing the pump to be used in processes, such as home brewing, that produce food products intended for human consumption.

The impeller assembly 21 can be produced as follows. The bushing 44 can be formed from a blank of resin-impregnated, carbon-graphite material. The blank can be machined into the cylindrical bushing 44, including the slots 47 and the chamfered surface 48, by a suitable process such as milling; and the passage 44 can be formed by drilling or other suitable means.

The impeller 22 can be overmolded onto the bushing 44. The impeller 22 can be formed by injection molding. In particular, the bushing 44 can be placed in a suitable mold, and liquid thermoplastic or thermosetting resin can be injected into the mold cavity so that the resin partially covers the exterior side surface 49 of the bushing 44. The mold cavity is shaped to define the outer contours of the body 25 and the blades 27.

The impeller 22 and the bushing 44 can be ejected from the mold once the resin has solidified to an extent that permits ejection. The inventors have found that subjecting the impeller 22 and the bushing 44 to a quick cool process immediately after ejection from the mold can substantially reduce the amount of volumetric shrinkage that occurs in the impeller 22 as the resin further cools and solidifies. For example, the quick cool process can be performed by immersing the impeller 22 and the bushing 44 in an ice bath having an initial temperature, i.e., a temperature at the time of initial immersion, at or below about 50° F., for a time period of about 60 seconds. The rapid cooling of the impeller 22 can be achieved by processes other than immersion in an ice bath.

Reducing the volumetric shrinkage of the impeller 22 can prevent the impeller 22 from cracking or otherwise damaging the brittle material from which the bushing 44 is formed. The inventors have found that, without such rapid cooling, it is not feasible to form the impeller 22 over the bushing 44 because the damage to the bushing 44 caused by the volumetric shrinkage of the impeller 22 will render the bushing 44 unusable.

The magnetic sleeve 23 can be inserted on the body 25 of the impeller 22 once the impeller 22 has fully cooled, to complete the production of the impeller assembly 21. 

We claim:
 1. A pump for transferring fluids, comprising: an electric motor comprising a rotatable output shaft; a pump housing having an inlet and an outlet; a shaft mounted on the pump housing; and an impeller assembly comprising: a bushing mounted for rotation on the shaft and comprising a resin-impregnated, carbon-graphite material; and an impeller comprising a body and a plurality of blades attached to the body, wherein: the impeller is mounted on the bushing, the impeller is magnetically coupled the output shaft of the electric motor so that the output shaft is operable to impart rotation to the impeller when the output shaft rotates; and the impeller is configured to pump the fluids between the inlet and the outlet of the housing as the impeller rotates.
 2. The pump of claim 1, wherein the impeller is magnetically coupled to the output shaft of the electric motor.
 3. The pump of claim 2, further comprising a magnet mechanically coupled to the output shaft of the electric motor so that the electric motor is operable to rotate the magnet; wherein the impeller assembly further comprises a magnetic sleeve mounted on the impeller and positioned within a magnetic field of the magnet so that the magnet is operable to impart rotation to the impeller assembly.
 4. The pump of claim 1, wherein the impeller comprises a plastic material.
 5. The pump of claim 1, wherein the bushing is substantially cylindrical.
 6. The pump of claim 5, wherein the bushing has a chamfered surface positioned between a side surface and a forward end of the bushing.
 7. The pump of claim 5, wherein the bushing has a substantially cylindrical internal passage extending between a forward and a rearward end of the bushing, and the passage is configured to receive the shaft.
 8. The pump of claim 7, wherein the bushing has two slots formed therein at diametrically-opposed locations on the forward end of the slot.
 9. The pump of claim 1, wherein the resin-impregnated, carbon-graphite material is a food grade material.
 10. The pump of claim 1, wherein the resin-impregnated, carbon-graphite material has a maximum operating temperature of at least about 500° F.
 11. The pump of clam 5, wherein the bushing has a substantially cylindrical exterior side surface, and the impeller encapsulates at least a portion of the exterior side surface.
 12. The pump of clam 11, wherein the impeller encapsulates a substantial entirety of the exterior side surface.
 13. The pump of claim 1, wherein the impeller is separated from the shaft by the bushing.
 14. A pump for transferring a fluids, comprising: an electric motor comprising a rotatable output shaft; a pump housing having an inlet and an outlet; a shaft mounted on the pump housing; and an impeller assembly comprising: a bushing mounted for rotation on the shaft and comprising a food-grade material having a maximum operating temperature of at least about 500° F.; and an impeller comprising a body and a plurality of blades attached to the body, wherein: the impeller is mounted on the bushing, the impeller is coupled the output shaft of the electric motor so that the output shaft is operable to impart rotation to the impeller when the output shaft rotates; and the impeller is configured to pump the fluids between the inlet and the outlet of the housing as the impeller rotates.
 15. The pump of clam 14, wherein the bushing material is resin-impregnated carbon-graphite.
 16. A process for producing an impeller assembly for a pump for transferring fluids, comprising: forming a bushing from a resin-impregnated, carbon-graphite material; and molding an impeller over the bushing.
 17. The process of claim 16, further comprising immersing the impeller and the bushing in an ice bath having an initial temperature of about 50° F. or below, for a time period of about 60 seconds.
 18. The process of claim 16, wherein forming a bushing from a resin-impregnated, carbon-graphite material comprises milling a blank of the resin-impregnated, carbon-graphite material.
 19. The process of claim 16, wherein molding an impeller over the bushing comprises placing the bushing in a mold and injecting molten resin into the mold.
 20. The process of claim 16, wherein the resin-impregnated, carbon-graphite material is a food-grade material having a maximum operating temperature of at least about 500° F. 